Optogenetics treats disease by directing light at neurons to temporarily turn them on or off. But for that technique to work in mice, researchers have had to make two big modifications to their biology. First, researchers have to tweak mice's genes (and would have to for human's genes as well) since neurons don't naturally respond to light. Second, they need to direct light deep into the brain, which has traditionally been done with obtrusive implants that require major surgery to put in place. So even though optogenetics could help people with many different medical conditions, it's understandable that they might be reluctant to receive such invasive procedures.